It is common to produce a phenolic resin foam by reacting, at ordinary temperature or by heating, a mixture in which a surfactant, a foaming agent, and a curing catalyst are mixed with a resol-type phenolic resin obtained by condensing phenol and formalin with an alkaline catalyst. In this case, a method in which the mixture is discharged on a surface material running at a constant speed and then formed into a sheet between conveyors in a curing oven is often used. The discharge method includes a method utilizing so-called tournament type distribution nozzles as proposed in Patent Literature 1. Further, there is a method which discharges the mixture integrally into a sheet utilizing a die as proposed in Patent Literature 2.